Friday, 22 July 2016

Kiribati has lost 80 % of its live corals in 10 months

El Nino is Basically Over — But this Global Coral Bleaching Event Just Won’t End

21 July, 2016

Back in 2014, an unsuspecting world was on the verge of a major global temperature increase. But despite warnings from scientists like Dr. Kevin Trenberth that deep ocean warming had sped up and would eventually result in rapid surface warming, the big media meme at the time was that global warming had ‘paused.’ Originating in The Economist, and swiftly spreading to numerous other news outlets, this particular blast of bad information fed the public a big helping of false sense of security.

In 2014 through 2016, maximum global temperatures jumped from around 0.65 degrees Celsius to around 1 C above the 20th-century average. In just three years’ time, the whole of the Earth’s surface had warmed by about 0.35 C. This is like cramming all of the warming from 1880 to 1980 into the three-year 2014-to-2016 period. Never before in all of the global climate record starting in the late 19th century has the Earth warmed so much in so short a time.

Leaving 20th Century Climate Behind
(Huge jump in global temperatures over the past three years has probably passed a number of climate thresholds — including temperature thresholds for key sea creatures like corals. Data Source: NOAA. Image source: Mashable.)

Global warming hadn’t paused at all. It was just getting ready to hit the accelerator.
Global Heat Spurs Bleaching, Mass Coral Mortality

All this newly-added surface heat represents a big step up into much warmer conditions for the global climate. What this means is that even the coolest months now will probably approximate the warmest months during the big super El Niño of 1998. Such a large temperature increase in so short a period means that the world has likely hit a number of tipping points for geophysical and ecological harm. One of the most visible of these tipping points involves an ongoing ecological crisis — a global coral bleaching event.
Perhaps the most vivid and heart-wrenching example of what is a very wide-ranging coral mortality situation is the bleaching-related damage to Australia’s Great Barrier Reef. In a terrible blow to one of the world’s most stunning natural wonders, about a quarter of the Great Barrier Reef’s corals have already been killed off — an event that some scientists say may eventually lead to 100 percent mortality of the Reef’s corals. (see a related report in The Guardian).

American Samoa Bleaching
(Coral bleaching events like this one in American Samoa during 2015 have been happening around the world since 2014. It’s a global event that’s still ongoing despite a turn toward La Niña conditions in the Pacific. This is the longest global coral bleaching event ever recorded, and one that could continue into 2017 or beyond. Image source: Nature.)

The Great Barrier Reef is not the only reef system to suffer. In fact, the added heat due to human-forced warming of the atmosphere and oceans has generated bleaching-induced heat stress and mass coral mortality the world over. And some of the world’s other great reef systems, including Kiribati, which lost 80 percent of its live corals in 10 months, have been hit so hard it’s doubtful they’ll ever recover.
The Seemingly Never-Ending Global Coral Bleaching Event

At issue is the fact that all this added global heat is creating a situation where reefs bleach year after year and, in some cases (as was the case with parts of the Great Barrier Reef this year) even bleach during winter. It’s a coral mass mortality that falls under the definition of a global bleaching event. But it’s also happening with an intensity, persistence, and duration that we’ve never seen before.
Beginning in 2014 with the big warm-up that preceded the 2015-2016 El Niño, the present global coral bleaching event is now, according to NOAA, the longest-running and the most extensive such event to have occurred in the modern record. NOAA notes:
the current global coral bleaching event is the longest ever recorded. It has affected more reefs than any previous global bleaching event and has been worse in some locales (e.g., Great Barrier Reef, Kiribati). Thermal stress during this event also has caused mass bleaching in several reefs that never bleached before (e.g., northernmost Great Barrier Reef).
Global coral bleaching event continues
(Global coral bleaching event extent as of July 20 according to NOAA. Note that sections of bleaching watch and warning conditions now extend across the northern edges of NOAA’s map, an indication that latitudinal extent of bleaching is expanding beyond typical ranges even as bleaching due to rising ocean temperatures appears to be becoming a near-constant issue for world corals. Image source: NOAA.)

NOAA had initially forecast that this very-long-duration bleaching event would end sometime in 2016 as El Niño faded out. However, with sea-surface temperatures in the equatorial Pacific hitting the cool side of natural climate variability in the form of La Niña-like conditions during recent weeks, and the current global coral bleaching event still going strong, one has to wonder if oceans have now become hot enough to spur widespread bleaching at almost any time.

NOAA now predicts a possible end to the current global bleaching event in 2017, giving the event a four-year duration. But with global temperatures continuing to warm, what we may be seeing is the start of an unbroken or nearly unbroken period of expanding coral bleaching, a time when global stress to corals due to high ocean temperatures is practically continuous.

Hat tip to June
Hat tip to Colorado Bob
Hat tip to DT Lange

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